A number of various methods have long been known for producing of ultra-dispersed carbon through processing of a natural gas, in particular, methane. It is a common knowledge that a natural gas includes, depending on the formation, 55-95 wt % of methane, 1-10 wt % of ethane, up to 10 wt % of propane-butane mixture, 1-10 wt % of C5 and higher hydrocarbons, and the balance nitrogen, carbon dioxide, sulfurous compounds, and helium.
There is described in U.S. Pat. No. 5,989,512 (IPC-6 C09C 1/48, published on Nov. 23, 1999) a method for producing of pure ultra-dispersed carbon by providing pyrolytic decomposition of hydrocarbons feedstock in a reaction chamber with the help of a plasma torch. Pyrolysis of methane in the reaction chamber results in the production of carbon and hydrogen.
The plasma torch provides for a predetermined temperature of from 1000° C. to 4000° C. in a reaction zone. Hydrogen is utilized as a process gas. Hydrocarbons are introduced into the reaction zone produced in a central axial part of the reactor chamber by means of injection nozzles provided tangentially in relation to the central axis of the reaction chamber.
The enthalpy value is maintained in the reaction zone at a predetermined level by adjusting the pressure in the reaction chamber within the range of from 1 bar to 3 bar, altering the feed rate of a plasma-forming gas (hydrogen) through the plasma torch and adjusting a angle of nozzles for introduction of hydrocarbons in relation to the central axis of the reaction chamber. It was found that the desirable quality of the produced ultra-dispersed carbon was dependent on the enthalpy value in the reaction zone.
Hydrogen produced during the process may be recirculated as a plasma-forming gas for the plasma torch. The prior art method allows the efficiency of conversion of hydrocarbons feedstock into a desired product—pure hydrogen to be substantially increased. The dispersity of carbon produced during implementation of the method did not, however, exceed 65 m2/g (with the degree of dispersity being defined as ratio of particles surface area to their weight).
In addition, the carbon particles produced with implementation of the prior art method have high poly-dispersion: the scatter in the values of effective specific surface area of the particles (dispersion) was up to 45%.
Also known is a method for producing of a technical-grade carbon (carbon black) from hydrocarbons feedstock, described in RU Patent No 2129578C1 (IPC-6, C09C 1/48, C090C 1/50, published on Apr. 27, 1999). This prior art method comprises a step of preliminary separation of hydrocarbons feedstock into close-cut fractions with a temperature gradient of from 10° C. to 40° C., which fractions are individually fed into the reaction chamber.
The heated close-out feedstock fractions are mixed into a heated hydrogen-containing gas and supplied to the torches. The mixture is combusted in the torches in the form of a diffusion laminar flame. The technical-grade carbon produced in the flame is deposited on a water-cooled deposition surface. The deposited technical-grade carbon is removed from the surface by means of scrapers and discharged from the apparatus.
Utilization of the close-cut fractions of hydrocarbons feedstock allows carbon to be produced which has an increased effective specific surface area. The given effect is due to the phenomenon of inhibiting the carbon black formation for the mixtures of hydrocarbons. However, with implementation of the method the specific surface area of carbon particles did not exceed 110 m2/g. The scatter in the specific particle surface area values was 13%.
A closest prior art to the claimed invention is a method for producing of carbon during chemical conversion of methane, said method being disclosed in RU Patent No 2172731C1 (IPC-7, C07C 11/02, C07C 2/82, published on Aug. 27, 2001). The method consists in oxidative coupling of methane and other natural gas components in the outer zone of a diffusion flame of a combustible while continuously discharging the chemical conversion products. The combustible and/or oxidizer are preliminarily heated to a temperature of from 500° C. to 1100° C. The process of oxidative coupling of methane is controlled by introducing into the reaction zone of non-combustible catalytically-inactive substances.
Hydrocarbons, in particular methane, are combusted in such a manner that one part thereof is burnt to produce a diffusion flame while the other part runs around the flame boundary to be converted on its outer boundary into desired products. The diffusion flame is generated upon combustion of methane between two streams of an oxidizer, which is preliminarily heated to a temperature exceeding the dissociation temperature for methane.
Combustion of methane is provided when it is available in an amount excessive in relation to an amount of oxidizer required for complete combustion of methane. The prior art method may use chlorine as an oxidizer with a volumetric methane to chlorine ratio of up to 100:1.
The mixed product obtained in the reactor as a result of synthesis and combustion is directed into a heat-exchanger and from there into a separator. The degree of methane conversion is approximately 75%. Unreacted methane is directed from the separator for a repeated conversion process. A dispersed chlorinated carbon is produced among other desired products.
However, implementation of the prior art method which is recognized as ineffective does not allow ultra-dispersed pure carbon to be produced with minimal scatter in the sizes of particles and the effective specific surface area value.